The projected research seeks to reassess the nature of the diversity of molecular species found in highly purified mouse interferon preparations. The dominant populations of Newcastle disease virus (NDV)- and poly rI:rC-induced L cell interferon will be isolated and separately purified by hydrophobic and immune affinity chromatography. Their constituent peptides, obtained on a preparative scale by thin slab gradient polyacrylamide gel, electrophoresis, will be studied with respect to the following properties: Rate of antiviral protection in homologous and heterologous cell cultures, growth inhibition, cytotoxicity, macrophage migration inhibition, endonuclease activity. Correlation between these biological properties and the prevalance of certain chemical groupings will be attempted by means of reagents which modify specific amino acid residues. The influence of peptide-cleaving reagents, sodium dodecyl sulfate, and glycosidases on the distribution of selected biological activities will also be studied. Serological relationships among interferon peptides will be examined in crossneutralization tests with the aid of immunoabsorbed sheep anti-mouse interferon globulins. Based on these results, 125I incorporation experiments and the development of a radioimmunoassay for interferon proteins will be undertaken. Finally, the distribution and activities of molecular components in interferons induced by NDV and poly rI:rC in different lines of mouse cells will be compared.